Fred, Mosaic Pins are used in knife making instead of plain solid brass or steel pins through the handle. They are made by setting small pieces of wire of various shapes and sizes into a steel, nickel silver or more commonly a brass tube. Set in place through the tube with resin these give what some folks think of as a more attractive finish to the job than a plain brass pin.
I don't have any pictures of them myself, but a browse through the knives on the Gallery will turn up a few examples I'm sure.